The present invention relates to roof control in underground mines such as coal mines, trona mines, and the like.
A detailed background and description of certain prior art is found in the allowed co-pending patent application entitled YIELDABLE MINE POST SYSTEM, Ser. No. 07/673,364 filed Mar. 22, 1991 and in the inventor's prior patent entitled YIELDABLE MINE POST, No. 5,015,125; the entire specifications and descriptions therein are fully incorporated herein by way of reference. For a rather extensive treatment as to the background of the art, the reader is respectfully referred to the incorporated patent.
Additional prior art made of record incited in the prosecution of the earlier case by the following patents:
______________________________________ U.S. Pat. Nos. 1006163 4100749 1538785 4302721 2036490 4344719 2532168 4382721 3877319 4995567 4006647 5015125 FOREIGN PATENTS 2045312 (Great Britain) 2904741 (Germany) ______________________________________
Both in this and in the inventor's prior patent, a telescoping tubular construction is provided. In the latter the innermost post length, mainly in tubular developed form, or simply a slotted tube, is provided, but with the inner tubular post being compressed and tack welded at its slot so that the innermost post length may be conveniently slid into and carried by the outermost post length. For mutual, wall-friction developing purposes, the inner tubular post length is inserted into the outer tubular post length, then the tack welds broken so that the innermost tubular post length expands radially outwardly so as to produce or commence a wall-friction characteristic desired. Subsequent insertion of a wedge in the slotted portion of the innermost tubular post length serves to increase the girth of the innermost tubular post length so as to result in the friction bubble needed, as fully explained in this above-referenced patent. The wall thicknesses of the innermost and outermost tubular post lengths of such prior patent are shown substantially enlarged for convenience of illustration.
The present invention takes the fundamental concept, as outlined in the prior patent and pending application a considerable step further in the provision of telescoping mine post lengths wherein, as a totally separate part, a friction bubble generator member is preliminarily inserted in the larger diameter post length in an interference-fit, radially loaded condition, and one of the ends of the tubular post length is made adjustable. In this way, the two lengths are separable, as well as the adjustable end, if desired, so that the disassembled post can be conveniently transported and re-assembled at the installation site without necessity of special tools to accomplish the aforementioned interference-fit at such site.